1. Field of the Invention
The present invention relates to an electrode material and methods for manufacturing the electrode material and an electrode, and more particularly to an electrode material having good properties such as heat resistance, electrical conductivity, heat conductivity, abrasion resistance and workability, and methods for manufacturing the electrode material and an electrode having the electrode material.
2. Prior Art
Concerning conventional electrodes such as special junction electrodes or spot resistance welding electrodes in order to join light metals or surface treatment steel sheets, the electrodes should have several properties including heat resistance, electrical conductivity, heat conductivity and abrasion resistance according their particular use. The electrode materials are also required such properties because the electrodes are made of the electrode materials. Furthermore, the electrode materials should have homogeneous structure and workability for forming the electrodes.
In general, the spot resistance welding electrode functions as a conductor for applying electricity to a material to be welded and a joining material for welding the material to be welded. Hence, the electrode having suitable properties are used as the spot resistance welding electrode in relation to the welding condition and the material to be welded. In most welding processes of the spot resistance welding electrodes, the spot resistance electrodes especially should have heat resistance and electrical conductivity at high temperature since the spot resistance electrodes are continuously subjected to the conditions of high temperature and high pressure. The electrode material should have low dispersity and should not fuse to the material to be welded as the spot resistance welding electrode which can be used under the condition of high temperature and high pressure for long periods.
Pure copper is mainly utilized as the conventional spot resistance welding electrode due to its high electrical conductivity and excellent consume resistance, however, the pure copper has defect of low mechanical strength. Therefore, in order to increase the strength of the pure copper, metals such as chrome (Cr), zirconium (Zr), silicon (Si), tungsten (W) or nickel (Ni) are added in small quantities to a base metal composed of the pure copper to form dispersion-hardening alloys which are utilized as the electrode materials. However, when the dispersion-hardening alloys composed of the above metals are used as the electrode materials, all of the required properties such as heat resistance, electrical conductivity, heat conductivity and abrasion resistance may not be present even though some properties may be partially present. For example, an alloy composed of copper-chrome is widely utilized as the spot resistance welding electrode and is manufactured by a typical casting method. In the alloy composed of copper as a base metal and by weight about 0.2% chrome, the copper-chrome alloy has enhanced mechanical strength because fine precipitated chrome is dispersed in the copper. However, when an electrode made of the copper-chrome alloy is welded to manufacture the spot resistance welding electrode, the thermal stability and abrasion resistance of the electrode made of the copper-chrome alloy are weakened because the precipitated chrome comes to have a large size by an arc-heat generated by the welding which takes place while the copper-chrome alloy is heated.
Therefore, a dispersion-hardening alloy composed of copper and metal oxide has been developed as an electrode material considering the problem of the copper-chrome alloy.
The dispersion-hardening alloy composed of copper and metal oxide includes a copper-aluminum oxide (Cu--Al.sub.2 O.sub.3), a copper-silicon oxide (Cu--SiO.sub.2), a copper-zirconium oxide (Cu--ZrO.sub.2) and so on. It is known that the copper-aluminum oxide alloy has excellent characteristics as the electrode material among the dispersion-hardening alloy composed of copper and metal oxide.
The copper-aluminum oxide alloy is manufactured by the combination of the powder metallurgy technique and the internal oxidation method, The copper-aluminum alloy has superior creep resistance, electrical conductivity and thermal stability at room temperature as well as at high temperature, so the copper-aluminum alloy is suitable as the electrode material.
However, it is difficult to control the degree of the internal oxidation of the copper-aluminum oxide alloy because the optimal quantity of a copper-oxide which is added as an oxidant is hardly controlled when the copper-aluminum oxide alloy is manufactured by the powder metallurgy technique and the internal oxidation method. Thus, an electrode made of the copper-aluminum oxide alloy has low mechanical strength when the electrode is made by using the copper-aluminum alloy and by the extrusion method, the drawing method or the forging method since the aluminum oxide doesn't be formed as a fine particle and homogeneously dispersed in the copper-aluminum oxide alloy.